Newspapers are produced predominantly according to the offset process. A plurality of paper webs are unwound from rolls, printed in the printing units and finally folded in the folding apparatus and cut. The inking can be set zone by zone in conventional inking systems. The presetting of the inking systems is based on the surface coverage of the printing plates, which is determined by means of so-called plate scanners, or can be calculated directly from the image data. The printer monitors the inking during the entire production and makes corrections in inking when necessary.
WO 96/12934 of Graphics Microsystems Inc., discloses a process for measuring the inking. In this or similar processes, a measuring element is recognized using video cameras and subjected to spectral measurement. The drawback of these processes is, first, the great technical effort and, second, the need to jointly print measuring elements on the web, which are subsequently cut off. The format of a newspaper is usually not trimmed, and it is therefore, in general, undesired to print measuring elements jointly. Therefore, such measurement processes or automatic ink regulating systems based on such processes have not yet been used in newspaper printing.
Another basic difficulty for the automatic regulation of inking arises from the complex dynamics of the conventional gap inking systems. For example, the inking must always be set zone by zone, the delay time with which an adjustment of the inking becomes effective on the printed web depends strongly on the ink take-off, and, moreover, the inking is affected in adjacent zones.
The production of printing plates is carried out in newspaper printing in the so-called preliminary printing stage. To do so, the original prepared in the editorial office of the newspaper is typically separated into four printing colors cyan, magenta, yellow and black. The color separations are reduced to half-tones after the separation, and pixel data, which represent the elements to be printed on the printing plate, which are exposed on the basis of these data, are obtained as a result.
Three-dimensional tristimulus values are transformed during the color separation into the four-dimensional color space C, M. Y, K. Depending on the type of separation, superimposed chromatic colors can be replaced to a certain extent or completely by black color. The type of separation should be known for corrections of the inking.
Changes also arise in the color effect of a paper web printed according to the web offset process when the amount of moisture fed in is changed. In fact, the establishment of a so-called ink-water balance requires a certain amount of experience in practice. Moreover, it depends on the type of paper and the printing style.
The visual evaluation of the color in the print is carried out in the three-dimensional color space, which corresponds to the human eye. On the other hand, there is a large number of adjusting possibilities to affect the color reproduction. As a result, the automatic regulation of the inking is made more difficult.
DE 198 22 662 A1 of MAN Roland Druckmaschinen AG proposes a process for operating a printing press, in which basic knowledge is obtained on the cooperation of operating media in the printing press by printing tests or during the production, it is stored in an expert system and used for the printing operation. An expert system is a “computer program system which stores all the material available on a special area, draws conclusions from same, and proposes solutions for problems of the area in question. The structure of expert systems and their use falls within the area of artificial intelligence” (cf. LexiRom 4.0, Microsoft Corp., 1999). Such systems typically have a dialog component, an explanation component, a knowledge acquisition component, a problem solving component, and a knowledge base. Such a system is difficult to operate and maintain. Besides the personnel for operating the printing press, it requires specialists from the area of information processing. An expert system is also not a closed regulatory circuit, it does not replace the expert, but is a tool to support the expert in processing complex problems by proposing solutions. To reduce the errors in the printing process, the applicant of the above-mentioned disclosure document proposes to reduce the complexity of the printing press by using a short inking system.